RF apparatus for controlled depth ablation of soft tissue

ABSTRACT

An RF ablation apparatus has a delivery catheter with a delivery catheter lumen and a delivery catheter distal end. A first RF electrode is positioned in the delivery catheter lumen. The first RF electrode has a distal end, RF conductive surface, and a lumen. A second RF electrode has a distal end. The second RF electrode is at least partially positioned in the lumen of the first catheter, with its distal end positioned at the exterior of the first RF electrode distal end. Additionally, the second RF electrode distal end has a geometry that permits it to be substantially a groundpad. The distal end of the first RF electrode is moved in a direction away from the second RF electrode distal end to create a painting effect of an ablation band or line between the two distal ends. Alternatively, the distal end of the second RF electrode can be moved in a direction away from the distal end of the first RF electrode. An RF insulative sleeve or coating is placed or positioned along a second RF electrode conductive surface where it is substantially adjacent to the first electrode conductive surface. An RF power source is coupled to the first and second RF electrodes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to an RF apparatus and the controlledcontraction of soft tissue, and more particularly, to an RF apparatusthat paints a line of ablation to achieve controlled contraction of softtissue.

2. Description of the Related Art

Instability of peripheral joints has long been recognized as asignificant cause of disability and functional limitation in patientswho are active in their daily activities, work or sports. Diarthrodialjoints of the musculoskeletal system have varying degrees of intrinsicstability based on joint geometry and ligament and soft tissueinvestment. Diarthrodial joints are comprised of the articulation of theends of bones and their covering of hyaline cartilage surrounded by asoft tissue joint capsule that maintains the constant contact of thecartilage surfaces. This joint capsule also maintains, within the joint,the synovial fluid that provides nutrition and lubrication of the jointsurfaces. Ligaments are soft tissue condensations in or around the jointcapsule that reinforce and hold the joint together while alsocontrolling and restricting various movements of the joints. Ligaments,joint capsule, and connective tissue are largely comprised of collagen.

When a joint becomes unstable, its soft tissue or bony structures allowfor excessive motion of the joint surfaces relative to each other, andin direction not normally permitted by the ligaments or capsule. Whenone surface of a joint slides out of position relative to the othersurface, but some contact remains, subluxation occurs. When one surfaceof the joint completely disengages and losses contact with the opposingsurface, a dislocation occurs. Typically, the more motion a jointnormally demonstrates, the more inherently loose the soft tissueinvestment is surrounding the joint. This makes some joints more proneto instability than others. The shoulder, glenohumeral joint, forexample, has the greatest range of motion of all peripheral joints. Ithas long been recognized as having the highest subluxation anddislocation rate because of its inherent laxity relative to moreconstrained "ball and socket" joints such as the hip.

Instability of the shoulder can occur congenitally, developmentally, ortraumatically and often becomes recurrent, necessitating surgicalrepair. In fact, subluxations and dislocations are a common occurrenceand cause for a large number of orthopedic procedures each year.Symptoms include pain, instability, weakness and limitation of function.If the instability is severe and recurrent, functional incapacity andarthritis may result. Surgical attempts are directed toward tighteningthe soft tissue restraints that have become pathologically loose. Theseprocedures are typically performed through open surgical approaches thatoften require hospitalization and prolonged rehabilitation programs.

More recently, endoscope (arthroscopic) techniques for achieving thesesame goals have been explored with variable success. Endoscopictechniques have the advantage of being performed through smallerincisions, and therefore are usually less painful. Such techniques areperformed on an outpatient basis, associated with less blood loss andlower risk of infection and have a more cosmetically acceptable scar.Recovery is often faster postoperatively than using open techniques.However, it is often more technically demanding to advance and tightencapsule or ligamentous tissue arthroscopically because of the difficultaccess to pathologically loose tissue, and because it is very hard todetermine how much tightening or advancement of the lax tissue isclinically necessary. In addition, fixation of advanced or tightenedsoft tissue is more difficult arthroscopically than through opensurgical methods.

Collagen connective tissue is ubiquitous in the human body anddemonstrates several unique characteristics not found in other tissues.It provides the cohesiveness of the musculoskeletal system, thestructural integrity of the viscera as well as the elasticity ofintegument. There are basically five types of collagen molecules, withType I being most common in bone, tendon, skin and other connectivetissues, and Type III is common in muscular and elastic tissues.

Intermolecular cross links provide collagen connective tissue withunique physical properties of high tensile strength and substantialelasticity. A previously recognized property of collagen is hydrothermalshrinkage of collagen fibers when elevated in temperature. This uniquemolecular response to temperature elevation is the result of rupture ofthe collagen stabilizing cross links and immediate contraction of thecollagen fibers to about one-third of their original lineal distention.Additionally, the caliber of the individual fibers increases greatly,over four fold, without changing the structural integrity of theconnective tissue.

There has been discussion in the existing literature regardingalteration of collagen connective tissue in different parts of the body.One known technique for effective use of this knowledge of theproperties of collagen is through the use of infrared laser energy toeffect tissue heating. The importance in controlling the localization,timing and intensity of laser energy delivery is recognized as paramountin providing the desired soft tissue shrinkage effects without creatingexcessive damage to the surrounding non-target tissues.

Shrinkage of collagen tissue is important in many applications. Oneapplication is the shoulder capsule. The capsule of the shoulderconsists of a synovial lining and three well defined layers of collagen.The fibers of the inner and outer layers extend in a coronal access fromthe glenoid to the humerus. The middle layer of the collagen extends ina sagittal direction, crossing the fibers of the other two layers. Therelative thickness and degree of intermingling of collagen fibers of thethree layers vary with different portions of the capsule. Theligamentous components of the capsule are represented by abruptthickenings of the inner layer with a significant increase in wellorganized coarse collagen bundles in the coronal plane.

The capsule functions as a hammock-like sling to support the humeralhead. In pathologic states of recurrent traumatic or developmentalinstability this capsule or pouch becomes attenuated, and the capsulecapacity increases secondary to capsule redundance.

In cases of congenital or developmental multi-directional laxity, analtered ratio of Type I to Type III collagen fibers may be noted. Inthese shoulder capsules, a higher ratio of more elastic type IIIcollagen has been described.

There exists a need for an apparatus to effect controlled ablation ofsoft tissue along a painted band or line created by the introduction ofRF energy. It would be desirable to provide an RF ablation apparatuswhich can provide controlled ablation depth of soft tissue to shrink thetissue to a desired state along a selectable surface, including but notlimited to a narrow line.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an RF ablationapparatus which creates controlled delivery of RF energy to a desiredtissue site. Another object of the present invention is to provide an RFablation apparatus which paints a band or line of ablation along aselected tissue site.

A further object of the present invention is to provide an RF ablationapparatus which includes a first RF electrode and a second RF electrode,with the first RF electrode being movable along an elongated portion ofthe second RF electrode to create a painting ablation of a selectedtissue site.

A further object of the present invention is to provide an RF ablationapparatus which provides selectable painting ablation of soft tissue.

Another object of the present invention is to provide an RF ablationapparatus which includes two RF electrodes, with one being slideablealong the other to create a painting ablation effect that can berepeated any number of times to achieve a desired level of tissueablation.

A further object of the present invention is to provide an RF ablationapparatus which includes two RF electrodes which have distal ends thatare positioned laterally in relation to a distal end of an associateddelivery catheter.

Yet another object of the present invention is to provide an RF ablationapparatus which includes two RF electrodes with distal ends, one of theRF electrode distal ends having a geometry and size sufficient to makeit substantially a ground pad.

Another object of the present invention is to provide an RF ablationapparatus with two RF electrodes with distal ends, and one of the distalends is radiused with substantially no sharp edges.

A further object of the present invention is to provide an RF ablationapparatus with two RF electrodes with distal ends, and one of the distalends has an RF conduction region that has a sharp edge.

Yet another object of the present invention is to provide an RF ablationapparatus which provides continuous, adjustable ablation of soft tissue.

A further object of the present invention is to provide an RF ablationapparatus which provides for the maximum amount of collagen contractionwithout dissociation of the collagen structure.

Yet another object of the present invention is to provide an RF ablationapparatus to deliver a controlled amount of RF energy to collagen softtissue of a joint in order to contract and restrict the soft tissueelasticity and improve joint stability.

These and other objects of the invention are obtained with an RFablation apparatus including, a delivery catheter, a delivery catheterlumen, and a delivery catheter distal end. A first RF electrode ispositioned in the delivery catheter lumen. The first RF electrode has afirst RF electrode distal end, a first RF electrode conductive surface,and a first RF electrode lumen. A second RF electrode, with a second RFelectrode distal end, is at least partially positioned in the first RFelectrode lumen. The second RF electrode distal end has a geometry thatpermits it to act substantially as groundpad. The first RF electrode ismoved away from the second RF electrode distal end, creating an ablationband or line between the distal ends of the two electrodes. An RFinsulative sleeve is positioned along a second RF electrode conductivesurface that is substantially adjacent to the first RF electrodeconductive surface. An RF power source is coupled to the first andsecond RF electrodes.

In another embodiment of the present invention, the RF ablationapparatus includes a delivery catheter with a delivery catheter lumen. Afirst RF electrode is positioned in the delivery catheter lumen. Thefirst RF electrode has a first RF electrode distal end with an RFconductive surface, and a first RF electrode lumen. A second RFelectrode has an elongated body that terminates at a second RF electrodedistal end with an RF conductive surface. The second RF electrode distalend has a diameter that is larger than the elongated body. The second RFelectrode is at least partially positioned in the first RF electrodelumen, with the second RF electrode distal end positioned at theexterior of the first RF electrode distal end. An ablation band or lineis created between the two distal ends of the electrodes as the first RFelectrode is moved in a direction away from the second RF electrodedistal end.

The second electrode distal end is radiused, and has substantially nosharp edges. A portion of the second electrode distal end can bepartially covered with an RF insulator. The first electrode distal endhas a sharp edge. Either one or both of the first and second electrodedistal ends can be deployed in a lateral direction relative to alongitudinal axis of the delivery catheter, permitting ablation indifficult to access areas, such as around hard objects.

Significantly, the first RF electrode distal end is movable in adirection away from the second RF electrode distal end. This creates aband of ablation. The size of the band is dependent of the relativesizes of the distal ends of the two electrodes. The depth of theablation is determined by the speed at which the first RF electrodedistal end is moved away from the second electrode distal end, as wellas the number of passes the first RF electrode distal end makes alongthe ablation band. These two parameters provide for continuousadjustable ablation to the selected tissue site.

The width of the ablation band is determined by the width of the firstelectrode distal end. Suitable sizes depend on the application andspecific tissue site.

Either one or both distal ends of the two electrodes can be deployed ina lateral direction relative to the delivery catheter. This is achievedthrough a variety of mechanisms including but not limited to, (i) a pullwire can be attached to the distal ends, (ii) the distal ends can beformed of a shaped memory metal, (iii) substantially all of the firstand second RF electrodes can be formed of a shaped memory metal, (iv)each electrode can include a resistive wire which, when heated, causesthe distal end of the respective electrode to be laterally deployed and(v) the distal ends of the first RF electrode and the delivery cathetercan be formed in a lateral direction relative to the longitudinal axisof the delivery catheter.

Movement of the first RF electrode distal end can occur in a number ofways. The first RF electrode can be attached to the delivery catheter.As the delivery catheter is moved away from the second RF electrodedistal end, the first RF electrode distal end is also moved, deliveringRF ablation energy in a painting-like manner. Additionally, the first RFelectrode can be slidably received in the lumen of the deliverycatheter. In this embodiment, the first RF electrode is moved away fromthe second electrode distal end independently of movement of thedelivery catheter. The same painting effect is achieved.

Portions of either one or both of the first and second electrode distalends can be partially covered with an RF insulator. This further definesthe size of the ablation band.

Optionally included with the ablation apparatus of the present inventionis a feedback device in response to a detected characteristic of all ora portion segment of the ablation band that provides a controlleddelivery of RF energy to the first and second electrodes. The detectedcharacteristic can be an impedance at a section of ablation band, atemperature profile of the ablation band, and the like.

The first RF electrode distal end can be rotated as it is moved in adirection away from the second RF electrode distal end, creating amulti-radiused ablation band. The first RF electrode distal end can bemoved any number of times away from the second RF electrode distal endin a painting like manner.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of the ablation apparatus of thepresent invention.

FIG. 2 is a perspective view of the second RF electrode distal end,illustrating in this embodiment that the distal end has radiused edges.

FIG. 3 is a perspective view of one embodiment of the first RF electrodedistal end with sharp edges.

FIG. 4 is a perspective view of a cylindrical first RF electrode with asharp edge distal end.

FIG. 5 is a perspective view of the second RF electrode, including agenerally elongated section of the electrode. An RF insulative coatingis on one side of the electrode distal end.

FIG. 6 is a perspective view of the first RF electrode, with a portionof the electrode covered by an RF insulative coating.

FIG. 7 is a perspective view of the ablation apparatus of the invention,including a handle associated with the delivery catheter, electricalconnectors, and a foot switch to activate the RF energy source.

FIG. 8(a) is a perspective view of the RF ablation device, with bothelectrodes extended laterally relative to the delivery catheter.

FIG. 8(b) is a cross-sectional view of the RF ablation device, with bothelectrodes extended laterally relative to the delivery catheter.

FIG. 9 is a cross-sectional view of the second RF electrode, including aresistive heating wire disposed in the lumen of the electrode.

FIG. 10 is a perspective view of the first RF electrode, including apull wire attached to the outer surface of the electrode.

FIG. 11 is a cross-sectional view of the first RF electrode, includingan RF insulator placed on the back surface of the electrode, andelectrolytic solution passing through the lumen of the electrode whichis then passed through an RF conductive surface to a selected tissuesite.

FIG. 12 is a block diagram of a system for delivering electrolyticsolution to a selected tissue site through the second RF electrode.

FIG. 13 is a cross-sectional diagram of a loose joint capsule.

FIG. 14 is a cross-sectional diagram of the RF ablation device of thepresent invention and a joint capsule. The first RF electrode is movedalong a surface of soft tissue and paints an ablation band.

FIG. 15 is a cross-sectional diagram of a disc with annulus fibrosis.

FIG. 16 is a cross-sectional diagram of the RF ablation apparatus of theinvention painting RF ablation energy along an ablation band.

FIG. 17 is a block diagram of a feedback device which can be associatedWith the RF ablation apparatus.

FIG. 18 is a circuitry block diagram of a feedback device of the presentinvention with a microprocessor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is an RF ablation apparatus that includes firstand second RF electrodes, a delivery catheter and an RF energy source.The first RF electrode is positioned in a lumen of the deliverycatheter. It has a distal end that extends beyond a distal end of thedelivery catheter. The second RF electrode is positioned in a lumen ofthe first RF electrode, and has a geometry that permits it to besubstantially a groundpad. It has a distal end that extends beyond thedistal end of the first RF electrode distal end. As the first RFelectrode is moved in a direction away from the second RF electrode, anablation band is created between the second and first RF electrodedistal ends. The first RF electrode can be moved any number of timesalong the ablation band in order to ablate more tissue. The ablationapparatus is particularly suitable for creating well defined ablationbands, of substantially even depth, along a tissue site, even indifficult to access tissue sites such as peripheral joints. Movement ofthe second RF electrode creates a painting of RF energy along a tissuesite. Again, the second RF electrode can be moved along the ablationband any number of times to provide numerous painting applications of RFenergy. The present invention provides for the continuous adjustableablation. The lesion created by the ablation is a painted line or bandalong the tissue. Depth control of ablation is controlled with speed ofmovement of the two distal ends of the electrodes away from each other.Additionally, continuous ablation can be achieved.

Referring now to FIG. 1, ablation apparatus 10 includes a deliverycatheter 12, first RF electrode 14 with a distal end 16, second RFelectrode 18 with a distal end 20 and an elongated body 22, and a sleeveof RF insulation 24 positioned along substantially the entire length ofelongated body 22. A handpiece 26 is associated with delivery catheter12. Insulation sleeve 24 can extend along only a desired portion ofelongated body 22, and can also cover a portion of second RF electrodedistal end 20. In one embodiment of the invention, the sizes of deliverycatheter 12, first RF electrode 14, first RF electrode distal end 16,second RF electrode distal end 20, and elongated body are in the rangeof about 0.5 to 10 mm respectively.

Delivery catheter 12, first RF electrode 14 and second RF electrode 18can be made of gold, aluminum, tungsten, nickel titanium, platinum,stainless, copper and brass.

The geometry and dimensions of second RF electrode distal end 20 areselected so that it serves as a groundpad in a bipolar mode ofoperation. Additionally, it may be preferred that second RF electrodedistal end 20 have a wider width than the width of elongated body 22.

First RF electrode 14 is moved in a direction away from second RFelectrode 18, as more fully described later in this disclosure. Further,second RF electrode 18 can be moved in a direction away from first RFelectrode 14. This creates a painting-type of affect, applying RFablative energy to a selected tissue site to create an ablation band.This is achieved by the bipolar ablation occurring between distal ends16 and 20, with second RF electrode distal end 20 serving as agroundpad. To achieve this result, it is desirable if second RFelectrode distal end 20 have no sharp edges, and that the edges 28 areradiused, as illustrated in FIG. 2. Further, all or a portion of firstelectrode distal edge 30 should be a sharp edge, as shown in FIG. 3.FIG. 4 illustrates an embodiment of first RF electrode 14 with asubstantially cylindrical geometry. It also has a sharp edge 30.

Referring now to FIGS. 5 and 6, portions of RF electrodes 14 and 18 caninclude an RF insulator 32 positioned on a portion of distal ends 16 and20. RF insulator 32 can, for example, be deposited on only one side ofdistal ends 16 and 20 so that there is an RF conductive surface on onlyone side of a distal end.

As illustrated in FIG. 7, delivery catheter 12 attaches to handle 26.Electrical cables 34 are coupled to first RF electrode 14, second RFelectrode 18 and to an RF energy source (not shown). A first actuator 36deploys movement of first electrode 14 in and out of delivery catheter12. This causes first electrode distal end 16 to move in a direction toand from second electrode distal end 20. First actuator 36 can alsodeploy the movement of delivery catheter 12. Alternatively, firstactivator can deploy movement of delivery catheter 12. When firstelectrode 14 is fixably positioned in the lumen of delivery catheter 12,the movement of first electrode 14, relative to the position of secondelectrode distal end 20, is determined by the slideable movement ofdelivery catheter 12 relative to second electrode distal end 20. Asuitable method of fixably positioning first electrode 14 in deliverycatheter is by attachment to handle 26. In either case, first electrodedistal end 16 is moved in a direction away from second electrode distalend 20, one or more times, to create an RF energy painting effect on thetissue, resulting in controlled shrinkage of the tissue, and collagenfibers without disrupting the structure of the collagen. Controlled,even ablation is achieved along a narrow band of a desired size.Suitable sizes of the band are about 0.5 to 10 mm.

A second actuator 38 is associated with pull wires that attach to distalends 16 and 20, or to other sections of first and second electrodes 14and 18 respectively. When tension is applied to the pull wires thiscauses distal ends 16 and 20 to deflect in a lateral direction relativeto a longitudinal axis of delivery catheter 12. A foot switch is coupledto the electrical cables associated with handle 26 and it activates theRF power source.

FIGS. 8(a) and 8(b) more fully illustrate the lateral deflection, andflexibility of first RF electrode 14 and second RF electrode 18.Electrodes 14 and 18 can be deflected by a variety of mechanismsincluding, (i) electrodes 14 and 18, or distal ends 16 and 20, can bemade of a shaped memory metal, such as NiTi, commercially available fromRayChem Corporation, Menlo Park, Calif., (ii) the use of pull wires orother similar devices, (iii) inclusion of a resistive wire in one orboth of electrodes 14 and 18 and (iv) inclusive of a heated fluid in oneor both of electrodes 14 and 18 that are formed of a deformable materialat elevated temperatures.

Lateral deflection of RF electrodes 14 and 18 is shown in FIG. 8 out ofthe distal end of delivery catheter 12. RF electrodes 14 and 18 can bedeployed up to 7 cm or greater. Additionally, RF electrodes 14 and 18can be laterally deployed up to about 90 degrees or greater. RFelectrodes 14 and 18 can be deployed sufficiently to reach arounddifficult to access areas such as discs of the spine, and aroundsurfaces of peripheral joints.

As previously mentioned, one method of laterally deploying RF electrodes14 and 18 is with the use of a resistive wire 40, illustrated in FIG. 9.Resistive wire may be placed in one or both of RF electrodes 14 and 18.Application of current, from a suitable current source, causesdeflection. The extent of the deflection is dependent on the type ofwire used, the amount of resistive wire 40 at any location, and theamount of current applied. Preferably, the greatest amount of resistivewire 40 is at distal ends 16 and 20.

As shown in FIG. 10, pull wire 41 can attach to a flat formed on theexterior of RF electrode 14. However, RF electrode 14 need not have aflat surface formed at its exterior. Additionally, pull wire 41 canattach to the interior of RF electrode 14. Pull wire 41 can similarly beattached to RF electrode 18. Wire EDM technology can be used to form theflat on RF electrode 14. Pull wire 41 need not be an actual wire. It canalso be a high tensile strength cord, such as Kevlar. Pull wire 41 canbe made of stainless steel flat wire, sheet material, and the like.

As shown in FIG. 11, an electrolytic solution or gel 42 can beintroduced through the lumen of first RF electrode 14 and delivered tothe selected ablation tissue site through fluid distribution ports 44formed in first electrode 14. In one embodiment, one side of first RFelectrode 14 is coated with an RF insulator 46, so that only theopposite side provides an RF energy conductive surface 48. It willappreciated that second RF electrode 18 can also include electrolyticsolution or gel 42 in a similar manner, as described above with first RFelectrode 14.

Referring now to FIG. 12, electrolytic solution or gel 42 is in aholding container 50, and transferred through a fluid conduit 52 to atemperature controller 54 which can cool and heat electrolytic solutionor gel 42 to a desired temperature. A pump 56 is associated with fluidconduit 52 to transfer fluid through the system and deliverselectrolytic solution or gel 42 to handpiece 26 to first and second RFelectrodes 14 and 18. Returning electrolytic solution or gel 42 ispassed to a waste container 58. The flow rate of electrolytic solution42 can be in the range of less than about 1 cc/min. to greater than 5cc/min.

Ablation apparatus 10 provides a method of painting a thin band ofablation along the surface of a body structure, including but notlimited to soft tissue. It also provides for the controlled contractionof collagen soft tissue. The collagen soft tissue is contracted to adesired shrinkage level without dissociation and breakdown of thecollagen structure. It can be used in the shoulder, spine, for cosmeticapplications, and the like. It will be appreciated to those skilled inthe art that ablation apparatus 10 has a variety of differentapplications, not those merely specifically mentioned in thisspecification. Some specific applications include joint capsules, suchas the gleno-humoral joint capsule of the shoulder, herniated discs, themeniscus of the knee, in the bowel, for hiatal hernias, abdominalhernias, bladder suspensions, tissue welding, DRS. and the like.

Ablation apparatus 10 delivers RF energy and thermal energy to softtissue such as collagen soft tissue. First RF electrode 14 is paintedacross the collagen soft tissue sequentially until the maximum shrinkageoccurs. In one embodiment, the collagen soft tissue is contracted in anamount of about two-thirds of its resting weight. A temperature range ofabout 43 to 90 degrees C. is preferred. More preferred, the temperaturerange is about 43 to 75 degrees C. Still more preferred is a temperaturerange of about 45 to 60 degrees C.

In one specific embodiment of the invention, joint capsules are treatedto eliminate capsular redundance. More specifically, ablation apparatus10 is utilized to contract soft collagen tissue in the gleno-humoraljoint capsule of the shoulder.

Ablation apparatus 10 provides an ablation band or line and accuratelycontrols the application of RF energy, within a specific thermal range,and delivers thermal energy to collagen soft tissue of, for instancejoints, thereby contracting and restricting the soft tissue elasticityand improving joint stability. When applied to the shoulder, there iscapsular shrinkage of the gleno-humeral joint capsule of the shoulderand a consequent contracture of the volume, the interior circumference,of the shoulder capsule to correct for recurrent instability symptoms.The degree of capsular shrinkage is determined by the operating surgeon,based on severity of preoperative symptoms and condition of the capsuleat the time of arthroscopic inspection.

In FIG. 13, a loose capsule is illustrated. Ablation apparatus 10 isapplied to a joint capsule in FIG. 14. First and second RF electrodes 14and 18 curve around the joint capsule to paint an ablation line ofcontrolled depth, causing the desired level of shrinkage. Figures 15 and16 illustrate the application of ablation apparatus 10 to a herniateddisc.

Referring again to FIG. 1, one or more impedance monitors 60 and thermalsensors 62 can be included with first RF electrode 14 or second RFelectrode 18. Impedance monitors 60 can be used to confirm, before anablation event, that good coupling of energy is achieved. Thermalsensors 62 are of conventional design, including but not limited tothermistors, thermocouples, resistive wires, and the like.

As illustrated in FIG. 17, a power supply 64 feeds energy into RF powergenerator (source) 66 and then to ablation apparatus 10. A multiplexer68 can be included to measure current, voltage and temperature.Multiplexer 68 is driven by a controller 70, which is a digital oranalog, or a computer with software. When controller 70 is a computer,it can include a CPU coupled through a system bus. This system caninclude a keyboard, a disk drive, or other non-volatile memory systems,a display, and other peripherals, as well known in the art. Also coupledto the bus are a program memory and a data memory.

An operator interface 72 includes operator controls 74 and a display 76.Controller 70 can be coupled to various imaging systems, transducers 60,thermal sensors 62, as well as viewing optics and fibers.

Current and voltage are used to calculate impedance. An operator setlevel of power and/or temperature may be determined, and this will notbe exceeded if desired. Controller 70 maintains the set level underchanging conditions. The amount of RF energy delivered controls theamount of power. A profile of power deliver can be incorporated incontroller 70, as well as a pre-set amount of energy to be delivered.

Feedback can be the measurement of impedance or temperature and occurseither at controller 70 or at RF source 66 if it incorporates acontroller. Impedance measurement can be achieved by supplying a smallamount of non-therapeutic RF energy. Voltage and current are thenmeasured to confirm electrical contact.

Circuitry, software and feedback to controller 70 result in full processcontrol and are used to change, (i) power (modulate) including RF,incoherent light, microwave, ultrasound and the like, (ii) the dutycycle (on-off and wattage), (iii) monopolar or bipolar energy delivery,(iv) fluid (electrolytic solution delivery, flow rate and pressure and(v) determine when ablation is completed through time, temperatureand/or impedance.

A block diagram of one embodiment of suitable processing circuitry isshown in FIG. 18. Thermal sensors 62 and transducers 60 are connected tothe input of an analog amplifier 78. Analog amplifier 78 can be aconventional differential amplifier circuit for use with thermistors andtransducers. The output of analog amplifier is sequentially connected byan analog multiplexer 80. Analog amplifier 80 can be a conventionaldifferential amplifier circuit for use with thermistors and transducers.The output of analog amplifier 78 is sequentially connected by an analogmultiplexer 80 to the input of an analog to digital converter 82. Theoutput of amplifier 78 is a voltage which represents the respectivesensed temperatures. Digitized amplifier output voltages are supplied byanalog to digital converter 82 to a microprocessor 84. Microprocessor 84calculates the temperature or impedance of the tissue. Microprocessor 84can be a type 68HCll. However, it will be appreciated that any suitablemicroprocessor or general purpose digital or analog computer can be usedto calculate impedance or temperature.

Calculated temperature and impedance values can be indicated on display76. Alternatively, or in addition to the numerical indication oftemperature of impedance, calculated impedance and temperature valuescan be compared by microprocessor 84 with temperature and impedancelimits. When the values exceed predetermined temperature or impedancevalues, a warning can be given on display 76. A control signal frommicroprocessor 84 can reduce the power level supplied by RF energysource 66, or deenergize the power delivered.

Thus, controller 70 receives and stores the digital values whichrepresent temperatures and impedances sensed. Calculated surfacetemperatures and impedances can be forwarded by controller 70 to display76.

The foregoing description of preferred embodiments of the presentinvention has been provided for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Obviously, many modificationsand variations will be apparent to practitioners skilled in this art.The embodiments were chosen and described in order to best explain theprinciples of the invention and its practical application, therebyenabling others skilled in the art to understand the invention forvarious embodiments and with various modifications, as are suited to theparticular use contemplated. It is intended that the scope of theinvention be defined by the following claims and their equivalents.

What is claimed is:
 1. An RF ablation apparatus, comprising:a deliverycatheter with a delivery catheter lumen and a delivery catheter distalend; a first RF electrode positioned in the delivery catheter lumen, thefirst RF electrode having a first RF electrode distal end, a first RFelectrode conductive surface, and a first RF electrode lumen; a secondRF electrode with a second RF electrode distal end and a second RFelectrode conductive surface, the second RF electrode being at leastpartially positioned in the first RF electrode lumen with the second RFelectrode distal end positioned at the exterior of the first RFelectrode distal end, the first RF electrode being movable in adirection away from the second electrode distal end creating an ablationbetween the second RF electrode distal end and the first RF electrodedistal end; an RF insulative sleeve positioned along a selected sectionof the second RF electrode conductive surface; and an RF power sourcecoupled to the first and second RF electrodes.
 2. An RF ablationapparatus, comprising:a delivery catheter with a delivery catheter lumenand a delivery catheter distal end; a first RF electrode positioned inthe delivery catheter lumen, the first RF electrode having a first RFelectrode distal end, a first RF electrode conductive surface, and afirst RF electrode lumen; a second RF electrode with a second RFelectrode distal end and a second RF electrode conductive surface, thesecond RF electrode being at least partially positioned in the first RFelectrode lumen with the second RF electrode distal end positioned atthe exterior of the first RF electrode distal end, the second RFelectrode distal end having a geometry that permits it to besubstantially a groundpad, the first RF electrode being movable in adirection away from the second electrode distal end creating an ablationbetween the second RF electrode distal end and the first RF electrodedistal end; an RF insulative sleeve positioned along a selected sectionof the second RF electrode conductive surface; and an RF power sourcecoupled to the first and second RF electrodes.
 3. The RF ablationapparatus of claim 1, wherein the RF insulative sleeve is positionedalong the second RF electrode conductive surface, and the second RFelectrode conductive surface is substantially adjacent to the firstelectrode conductive surface.
 4. The RF ablation apparatus of claim 2,wherein the distal end of the second electrode is radiused.
 5. The RFablation apparatus of claim 2, wherein the distal end of the secondelectrode has radiused edges.
 6. The RF ablation apparatus of claim 2,wherein at least a portion of the first electrode distal end has a sharpedge.
 7. The RF ablation apparatus of claim 2, wherein the firstelectrode distal end has a non-radiused edge.
 8. The RF ablationapparatus of claim 2, further comprising:a pull wire attached to thefirst electrode.
 9. The RF ablation apparatus of claim 2, furthercomprising:a pull wire attached to the second electrode.
 10. The RFablation apparatus of claim 2 wherein the first electrode distal end isdeployed laterally in relation to the distal end of the deliverycatheter.
 11. The RF ablation apparatus of claim 2, wherein the firstelectrode distal end is made of a memory metal.
 12. The RF ablationapparatus of claim 2, wherein the second electrode distal end isdeployed laterally in relation to the distal end of the deliverycatheter.
 13. The RF ablation apparatus of claim 2, wherein the secondelectrode distal end is made of a memory metal.
 14. The RF ablationapparatus of claim 2, wherein the first electrode is slidably movablealong the lumen of the delivery catheter.
 15. The RF ablation apparatusof claim 2, wherein the first electrode is fixably positioned with thedelivery catheter and movable with movement of the delivery catheter.16. The RF ablation apparatus of claim 2 wherein the first electrode ispartially RF insulated.
 17. The RF ablation apparatus of claim 2,wherein at least a portion of the first electrode distal end is RFinsulated.
 18. The RF ablation apparatus of claim 2, wherein at least aportion of the second electrode distal end is RF insulated.
 19. The RFablation apparatus of claim 2, wherein the first electrode is fixed inrelation to the delivery catheter.
 20. The RF ablation apparatus ofclaim 2, wherein the first electrode is articulated in relation to thedelivery catheter.
 21. The RF ablation apparatus of claim 2, wherein thesecond electrode is fixed in relation to the delivery catheter.
 22. TheRF ablation apparatus of claim 2, wherein the second electrode isarticulated in relation to the delivery catheter.
 23. An RF ablationapparatus, comprising:a delivery catheter with a delivery catheterlumen; a first RF electrode positioned in the delivery catheter lumen,the first RF electrode having a first RF electrode distal end with an RFconductive surface, and a first RF electrode lumen; a second RFelectrode including an elongated body that terminates at a second RFelectrode distal end with an average diameter larger than an averagediameter of the elongated body, the second RF electrode being at leastpartially positioned in the first RF electrode lumen with the second RFelectrode distal end positioned at the exterior of the first RFelectrode distal end, the first RF electrode being capable of movementin a direction away from the second RF electrode distal end to create anablation band between the distal end of the second RF electrode and thefirst RF electrode distal end; and an RF power source coupled to thefirst and second RF electrodes.
 24. The RF ablation apparatus of claim23, further comprising:an RF insulative sleeve positioned along theelongated body of the second RF electrode.
 25. The RF ablation apparatusof claim 24, wherein at least a portion of the second electrode distalend is RF insulated.
 26. The RF ablation apparatus of claim 23, whereinthe distal end of the second RF electrode has a geometry and size makingit substantially a groundpad.
 27. The RF ablation apparatus of claim 23,wherein the second electrode distal end is radiused.
 28. The RF ablationapparatus of claim 23, wherein the second electrode distal end hasradiused edges.
 29. The RF ablation apparatus of claim 23, wherein thefirst electrode distal end has a sharp edge.
 30. The RF ablationapparatus of claim 23, wherein the RF conductive surface of the firstelectrode distal end has a sharp edge.
 31. The RF ablation apparatus ofclaim 23, wherein the RF conductive surface of the first electrodedistal end has a non-radiused edge.
 32. The RF ablation apparatus ofclaim 23, further comprising:a pull wire attached to the firstelectrode.
 33. The RF ablation apparatus of claim 23, wherein the firstelectrode distal end is deployed laterally in relation to a longitudinalaxis of the delivery catheter.
 34. The RF ablation apparatus of claim23, wherein the first electrode distal end is made of a memory metal.35. The RF ablation apparatus of claim 23, wherein the second electrodedistal end is deployed laterally in relation to a longitudinal axis ofthe delivery catheter.
 36. The RF ablation apparatus of claim 23,wherein the second electrode distal end is made of a memory metal. 37.The RF ablation apparatus of claim 23, wherein the first electrode isslidably movable along the lumen of the delivery catheter.
 38. The RFablation apparatus of claim 23, wherein the first electrode is fixablypositioned to the delivery catheter and movable with a movement of thedelivery catheter.
 39. The RF ablation apparatus of claim 23, whereinthe first electrode is at least partially RF insulated.
 40. The RFablation apparatus of claim 23, wherein at least a portion of the firstelectrode distal end is RF insulated.
 41. The RF ablation apparatus ofclaim 23, wherein at least a portion of the second electrode distal endis RF insulated.
 42. The RF ablation apparatus of claim 23, furthercomprising:a feedback device in response to a detected characteristic ofthe ablation band that provides a controlled delivery of RF energy tothe first and second electrodes.
 43. The ablation apparatus of claim 42,wherein the detected characteristic is an impedance at a section of theablation band.
 44. The ablation apparatus of claim 42, wherein thedetected characteristic is a temperature profile at a section of theablation band.